The present invention relates to an automatic traveling vehicle, and in particular, to an automatic traveling vehicle with an object detector that can travel at high speed without colliding or interfering with a detected object.
There exists an automatic traveling vehicle comprising a directional medium receiver and transmitter means to radiate a directional medium (for example, light, a millimeter wave, or an ultrasonic wave) and receive a reflected wave from an object in a direction consistent with vehicle travel; an actuator for changing the direction of radiation of the directional medium, which is mounted on the directional medium receiver and transmitter means; and an object detector for analyzing an object detection status after receiving a reflected wave from an object transmitted by the directional medium receiver and transmitter means.
The directional medium receiver and transmitter means comprises a light transmitting unit and a light receiving unit if the directional medium is light, for example, or comprises a transmitting and receiving antenna if the directional medium is a millimeter wave or an ultrasonic wave. The actuator for changing the direction of radiation of the directional medium is a scanner which allows the directional medium to be directed at an angle within a predetermined angular range by, for example, pivoting the directional medium receiver and transmitter means. The object detector receives reception and transmission information (in other words, a frequency, a reception and transmission strength, and the like) regarding the directional medium produced and received by the directional medium receiver and transmitter means. The object detector further analyzes an object detection status (in other words, whether or not any object is detected, a distance to an object, a relative speed to an object, and the like). The analysis results are entered into a separate control unit having a stored control program. In accordance with the control program, the control unit controls the speed of the vehicle by operating an alarm or by operating a vehicle speed control actuator (for example, an accelerator or a brake). This prevents the vehicle from colliding with the detected object and from interfering with it.
Japanese Unexamined Patent Publication (A) No. 5-203746 discloses an actuator for changing the direction of radiation of the directional medium based on a steering operation, where a directional medium receiver and transmitter means is rotated so as to match a directional medium with a steering angle. This actuator has the following problems.
(1) In a curved course Cc, as shown in FIG. 7, a directional medium A is emitted along a curvature of the curved course Cc in accordance with a steering angle. A detection area to be treated by an object detector is area AC1, formed by overlapping regions of a directional medium A and the indicated area XC of course C followed by vehicle 1, which does not include areas further along course Cc.
(2) In an irregularly curved course Cs, as shown in FIG. 8, a directional medium A is emitted along a curvature of a first curve Cc. Due to steering angle limitations, a detection area AC1 does not include areas further along course Cs.
(3) In a straight course Ct, as shown in FIG. 9, supposing a misaligned vehicle 1 is subject to a steering operation to return the vehicle 1 to the center of course Ct, the steering angle causes a radiated directional medium A to be directed toward the edge of course Ct. Thus, a detection area AC1 does not include areas further along course Ct.
In this type of an automatic traveling vehicle, a vehicle control and other operations are performed on the basis of the effective detection area AC2, and the effective detection area AC2 is often a short distance; therefore, control of the vehicle 1 is forced to be performed at a low speed. Accordingly, for an unmanned dump truck that must travel, for example, in a mine, improved productivity cannot be expected.
For any of the above cases, an effective detection area AC2 may extend further than the detection area AC1 if the directional medium A is pivoted by an actuator for changing the direction of radiation of the directional medium. The region defined by reference character X (see FIGS. 7-9), or the critical detection region X, designates the maximum pivoting range of the directional medium A using an actuator for changing the direction of radiation of the directional medium.
In view of these problems in the prior art, it is an object of the present invention to provide an automatic traveling vehicle with an object detector which can travel at high speed in a predetermined course without colliding or interfering with an object detected by an object detector.
According to a first aspect the present invention, there is provided an automatic traveling vehicle with an object detector having a directional medium receiver and transmitter means for radiating a directional medium (for example, light, a millimeter wave, or an ultrasonic wave) in a traveling direction of the automatic traveling vehicle and receiving a reflected wave from an object; an actuator for changing the direction of radiation of the directional medium, and an object detector for analyzing an object detection status after receiving a reflected wave from an object transmitted by the directional medium receiver and transmitter means. The automatic traveling vehicle further includes a predetermined course storage means for storing a predetermined course in a coordinate system; a critical detection area storage means for storing a critical detection area in a coordinate system, the critical detection area being created by direction of the directional medium through a maximum angular range using the actuator for changing the direction of radiation of the directional medium; a current position determining means for determining the current portion of the automatic traveling vehicle in the predetermined course based on course information from the predetermined course storage means; and a calculator means.
The calculator means receives course information from the predetermined course storage means, critical detection area information from the critical detection area storage means, and the current position information of the automatic traveling vehicle from the current position determining means. Using this information, the calculator means determines the farthest portion from the current position of the automatic traveling vehicle in a region defined by the overlapped areas of the critical detection area and the predetermined course. The calculator then outputs a signal to the actuator for changing the direction of radiation of the directional medium so that a radiated direction of the directional medium corresponds to the farthest portion.
According to the above configuration, the automatic traveling vehicle is capable of evaluating the greatest effective detection area. Thus, the automatic traveling vehicle can travel at high speed without colliding or interfering with a detected object.
According to a second aspect of the present invention based on the first aspect thereof, an automatic traveling vehicle includes each of the features set forth above. The automatic traveling vehicle further includes a vehicle speed control actuator to control the speed of the automatic traveling vehicle; an actual vehicle speed detector means to detect an actual vehicle speed; and a predetermined vehicle speed storage means to store predetermined vehicle speed information for each position along the predetermined course.
The calculator means receives actual vehicle speed information from the actual vehicle speed detector means and predetermined vehicle speed information from the predetermined vehicle speed storage means. The calculator outputs an operation signal to the vehicle speed control actuator so that the actual vehicle speed matches the predetermined vehicle speed information, calculates a distance from the current position of the automatic traveling vehicle to the calculated farthest portion, calculates a vehicle speed at which the vehicle can stop in this distance, and renews the predetermined vehicle speed information in the predetermined vehicle speed storage means to a vehicle speed equal to or lower than this vehicle speed.
According to this configuration, a predetermined vehicle speed is automatically renewed to a vehicle speed at which a vehicle can stop in a detected distance. Thus, the automatic traveling vehicle can be controlled more reliably from colliding or interfering with a detected object.